REMOVAL DEVICE FOR A MILKING MEANS AND A SLIDING VANE MOTOR FOR THE OPERATION THEREOF

Abstract: A device for automatic removal of a milking means comprises an actuation means (2) having a rotatable cord drum (20) with a cord (13). The actuation means (2) comprises a pneumatically operated sliding vane motor (19) provided to turn the cord drum (20) for winding the cord (13) thereon. The sliding vane motor (19) comprises a housing (33). A rotor body (R) and at least a pair of vanes (26, 28) form a first and a second radially directed circular cylindrical sealing surface (G, G'). The housing forms a first and a second circular cylindrical sealing surface (44, 45). The sliding vane motor has a first and a second sealing means (S, S'), respectively, provided for sealing between said first and said second sealing surface (G, G', 44, 45) of the rotor body (R) and the housing (33), respectively.

Description: Removal device for a milking means and a sliding vane motor for the operation thereof FIELD OF THE INVENTION The present invention relates to a sliding vane motor comprising a housing forming a cylindrical chamber with a mantle wall, a rotor body journalled eccentrically in the cylindrical chamber, and at least a pair of vanes arranged radially movable in recesses in the rotor body for sealing against the chamber ' s mantle wall so that at least two rotor chambers are formed, which rotor body forms a first, radially directed circular cylindrical sealing surface, situated axially relative to the rotor body on one side of the vanes, and a second, radially directed circular cylindrical sealing surface, situated axially relative to the rotor body on the other, opposite side of the vanes, which housing forms a first circular cylindrical sealing surface extending in the rotor body's circumferential direction and surrounding said first sealing surface of the rotor body, and a second circular cylindrical sealing surface extending in the rotor body's circumferential direction and sur¬ rounding said second sealing surface of the rotor body, wherein said sealing surfaces being coaxial with the rotor body. The invention also relates to a device for automatic removal of a milking means from the teats of an animal after finished milking, which device comprises a sliding vane motor of the above stated kind. BACKGROUND OF THE INVENTION Such a removal device and such a sliding vane motor are known from WO 93/00002. The known removal device is compact and is therefore particularly suitable for portable milking equipment for serving tied up cows. However, the known removal device has proven to be unreliable during operation since leakage of air may occur between the rotor chambers in the sliding vane motor to such an extent that the power output of the motor will be poorer than desired or, in the worst case, the sliding vane motor ceases to function. An object of the present invention is to provide a sliding vane motor with an insignificant leakage of air between the rotor chambers without causing the sliding vane motor to be more expensive to produce than the known sliding vane motor. Yet another object of the invention is to provide a removal device for automatic removal of a milking means which is more reliable in operation than the known removal device. These objects are achieved by means of a sliding vane motor and a removal device, respectively, of the initially described kind, which both are characterized in that a first separate sealing means is provided for sealing between said first sealing surfaces of the rotor body and the housing, respectively, and in that a second separate sealing means is provided for sealing between said second sealing surfaces of the rotor body and the housing, respectively, and in that the first and the second sealing means comprise a first and second ring, respectively, of a hard, resilient material, each ring presenting a discontinuation in the circumferential direction of the ring. Hereby is achieved that the rotor body and the housing of the sliding vane motor can be produced with rela¬ tively low demands of tolerances, whereby the production costs can be kept down, at the same time as the leakage between the rotor chambers can be considerably reduced. Furthermore is achieved a reduced friction between the rotor and the housing of the sliding vane motor, reducing the wear of the sliding vane motor during operation. Preferably each ring forms two free, opposite ends in the area of said discontinuation, the said free ends being situated at a distance from each other when the ring is unmounted. Two advantages are thus achieved; firstly the ring is easy to mount when the sliding vane motor is to be assembled; secondly the discontinuation of the ring will be reduced or totally disappear so that the sealing properties of the ring are improved when a negative pressure is applied onto the motor, i.e. the ring will seal during operation. Conveniently, the rings are substantially circular and dimensioned such that they are pressed together somewhat by the circular cylindrical sealing surfaces of the housing, so that the opposite ends of the respective ring are situated closer to each other than when the rings are unmounted. Suitably, the first and the second sealing surfaces of the rotor body have a diameter which is different from the diameter of the rotor body. DRAWING SUMMARY The sliding vane motor and the removal device, respec¬ tively, according to the invention is described closer in the following with reference to the annexed drawings, in which Figure 1 shows a milking equipment with a removal device according to the invention, Figure 2 shows a side view of an actuation means com¬ prising a motor, a reduction gear and a cord drum of the removal device according to figure 1, Figure 3 shows a view from above of the actuation means according to figure 1, Figure 4A shows a view of a longitudinal section through the actuation means according to figure 2, Figure 4B shows a sealing means and figure 5 shows a view of a section along the line V-V in figure 4A. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The milking equipment shown in figure 1 comprises a stand 1, to which an actuation means 2 and a control means 3 are attached. The stand 1 is suspensible by means of a hook 4 on existing pipelines, for example a vacuum pipeline 5. From a milking means 6, comprising four teat cups 7 and a milk claw 8, a milk tube 9 and a pulsation tube 10 extend to a milk flow meter 11 and a pulsation means 12, respectively, which are hooked by the stand 1. A cord 13 extends from the actuation means 2 to the milk claw 8 and is connected thereto by means of a connection means 14. From the milk flow meter 11 and the pulsator 12, a milk tube 15 and an air tube 16, respectively, extend upwards to a coupling means 17 arranged on a milk pipeline 18. The upper ends of the tubes 15 and 16 are provided with means for quick connection to the coupling means 17, adapted to connect the milk tube 15 and the air tube 16 to the milk pipeline 18 and the vacuum pipeline 5, respectively. The actuation means 2 comprises (see figure 4A) a sliding vane motor 19, a cord drum 20 and a planetary gearing 21, which interconnects the sliding vane motor 19 and the cord drum 20. The sliding vane motor 19 has a rotor body R, comprising a rotor shaft 22 with a circular cylindrical mantle 23. In the mantle 23, four radial recesses 24 are arranged as two pairs of opposite recesses 24 extending perpen¬ dicularly to each other. Four vanes 25-28 are dis- placible in the respective recess 24, each pair of opposite vanes 25, 27 and 26, 28, respectively, abutting one another via spacing means in the form of two cylindrical pins 29, 30 and 31, 32, respectively. Thus, each pair of vanes 25, 27 and 26, 28, respectively, including their belonging pins 29, 30 and 31, 32, respectively, form a radially displacible means relative to the rotor shaft. Of course, the mantle 23 need not be homogenous between the recesses. Accordingly, the mantle 23 does not necessarily comprise a wall, as shown in figure 5, but could as well be an imaginary shell, i.e. the wall between the recesses 24 may have any desired form, as long as it does not extend outside the imaginary circular cylindrical shell forming the mantle 23. Alter- natively, the mantle wall may be excluded so that the rotor body R only comprises the walls forming the radial recesses 24, and the rotor shaft 22. Furthermore, the sliding vane motor 19 has a housing 33 forming a cylindrical rotor chamber 34, in which the rotor shaft 22 extends parallel with the centre axis of the rotor chamber 34. The extension of the cylindrical rotor chamber 34 across the rotor shaft 22 is substan- tially constant along the circumference of the rotor chamber 34, which gives the rotor chamber 34 a slightly oval cross-section. The rotor chamber 34 is divided by the vanes 25-28 in four separate chambers 35-38 oriented next to each other about the rotor shaft 22. The vanes 25-28 seal against the cylindrical wall of the rotor chamber 34 by means of resilient sealing strips 39 arranged on the radially outer edges of the vanes 25-28, respectively. Each recess 24 is axially delimited by two opposite walls 40, 41 with radial outer ends, constituting parts of a first and a second circular cylindrical surface 42, 43 of the mantle 23. The housing 33 is shaped with a first and a second circular cylindrical sealing surface 44, 45 situated concentrically with the rotor shaft 22 and radially aligned with the first and second circular cylindrical surfaces 42, 43, respectively of the mantle 23. A part of the mantle's first and second circular surfaces 42, 43, respectively, is provided with an annular groove forming a first and a second circular cylindrical sealing surface (G, G' ), which are concent- rical with and have a smaller diameter than the first and second circular cylindrical surfaces 42, 43, respec¬ tively, of the rotor's mantle 23. Thus, said groove forms an annular interspace between the first and second circular cylindrical sealing surface G, G', respec¬ tively, of the rotor and the first and the second circular cylindrical sealing surface 44, 45, respec¬ tively, of the housing 33 of the sliding vane motor. In the respective interspace a sealing means S, S' is provided. Certainly, it would also be possible to form the grooves in the housing 33 instead of in the rotor's mantle 23 in order to make room for the sealing means S, S'. Each sealing means S, S' consists of a ring made of a hard, resilient material, such as acetaldehyde plastics (POM). The respective sealing ring S, S' presents a discontinuation D in the circumferential direction of the ring, such that ends El and E2 are formed (see figure 4B) . In its unloaded state, the respective sealing ring S, S' has a larger diameter than the first and the second circular cylindrical sealing surfaces 44, 45, respectively, of the housing. During mounting of the sealing rings S, S' on its respective sealing surface 44, 45, the ends El, E2 of the respective sealing ring are pressed together such that the respective sealing ring can be mounted on its respective sealing surface 44, 45. The sealing rings S, S' are now held in place by means of the inherent spring action of the material. The ends El, E2 are situated close to each other, but with¬ out touching each other. Owing to the discontinuation D of the respective sealing ring S, S 1 they can in an easy way be mounted in the sliding vane motor. Of course, the discontinuation D need not be as shown in figure 4B, it could as well be formed between over¬ lapping end positions. The housing 33 has an inlet means 46 for atmosphere. The inlet means 46 is connected to the rotor chamber 34 via an inlet passage 47. Furthermore, the housing 33 has an outlet means 48 for connection to a vacuum source. The outlet means 48 is connected to the rotor chamber 34 via an outlet passage 49. One end of the rotor shaft 22 is provided with a sun wheel 50, which constitutes a part of the planetary gearing 21, which is also provided with a crown wheel 51. Three planet wheels 52 are journalled on the cord drum 20 on the same radial distance from the rotary axis of the cord drum 20 and is engaged with the sun wheel 50 and the crown wheel 51. The gear ratio of the planetary gearing 21 is 1:5, which, hence, means that the rotor shaft 22 of the sliding vane motor 19 rotates five turns for each turn that the cord drum 20 is rotated. The cord drum 20 has a connection means 53, by means of which one end of the cord 13 may be clamped so that the cord 13 is held tight against the drum 20. The housing 33 is formed with an opening 54, through which the cord 13 can pass during winding and unwinding of the cord 13 on the cord drum. The removal device works in the following way: Firstly, the milker suspends the milking equipment on the vacuum pipeline 5 by means of the hook 4 in the vicinity of the cow to be milked. Then the milker takes the milk means 6 from the stand 1 and brings it to the cow's teats, wherein the cord 13 is unwound from the cord drum 20. Since the sliding vane motor 19 at this stage is not activated, it only exerts a minor braking resistance on the cord drum 20 during the unwinding of the cord 13 from the cord drum 20. When the milker has applied the teat cups 7 onto the teats of the cow the milking starts, wherein extracted milk passes through the milk claw 8, the milk tube 9, the milk flow meter 11, the milk tube 15 and into the milk pipeline 18 via the coupling means 17. In the final stage of the milking, the milk flow meter 11 senses the ceasing milk flow and emits a signal to the control means 3, which activates the sliding vane motor 19 by connecting the outlet means 48 to the vacuum pipeline 5 via the air tube 16. Hereby, a negative pressure is created in the outlet passage 49 and in the separate chambers, which for the moment are communica- ting with the outlet passage 49. In the position of rotation shown in figure 5, a negative pressure accor¬ dingly arises in the chambers 35 and 38 resulting in that the rotor shaft 22 is rotated counter-clockwise. The cord drum 20 is hereby turned by the rotor shaft 22 via the planetary gearing 21, so that the cord 13 is wound onto the cord drum 20 and pulls the milking means 6 off the cow ' s teats. When the cord 13 has been completely wound onto the cord drum 20, the sliding vane motor 19 is still activated until the milker has hung up the milking means 6 on the stand. Alternatively, the cord 13 may be provided with a blocking means, which blocks the cord from being unwound from the cord drum 20 when the sliding vane motor is inactivated. In this case the milker must lift off the blocking means in connection with next milking occasion. Thereafter, the milker can take the hook 4 and the tubes 15 and 16 from the vacuum pipeline 5 and the coupling means 17, respectively, and carry the milking equipment to the next cow to be milked. During operation of the sliding vane motor, the ends El, E2 of the respective sealing ring S, S' will be pressed together by the applied negative pressure so that the ends El, E2 abut. In this way an improved sealing during operation is achieved.

Claims: Claims 1. Sliding vane motor comprising a housing (33 ) forming a cylindrical chamber (34) with a mantle wall, a rotor body (R) eccentrically journalled in the cylindrical chamber (34), and at least a pair of vanes (25-28) arranged radially movable in recesses in the rotor body (R) for sealing against the mantle wall of the chamber so that at least two rotor chambers (35-38) are formed, which rotor body (R) forms a first, radially directed circular cylindrical sealing surface (G), situated axially relative to the rotor body on one side of the vanes, and a second, radially directed circular cylindrical sealing surface (G 1 ), situated axially relative to the rotor body on the other, opposite side of the vanes, which housing forms a first circular cylindrical sealing surface (44) extending in the rotor body's circumferential direction and surrounding said first sealing surface (G) of the rotor body (R), and a second circular cylindrical sealing surface (45) extending in the rotor body ' s circumferential direction and surrounding said second sealing surface (G' ) of the rotor body (R), said sealing surfaces (44, G, 45, G' ) being coaxial with the rotor body (R), c h a r a c - t e r i z e d i n that a first separate sealing means (S) is provided for sealing between said first sealing surfaces (G, 44) of the rotor body (R) and the housing (33), respectively, and in that a second separate sealing means (S' ) is provided for sealing between said second sealing surfaces (G', 45) of the rotor body (R) and the housing (33), respectively, and in that the first and the second sealing means comprise a first and a second ring (S, S'), respectively, of a hard, resilient material, each ring presenting a dis- continuation (D) in the circumferential direction of the ring. 2. Sliding vane motor according to claim 1, c h a ¬ r a c t e r i z e d i n that each ring (S, S' ) forms two free, opposite ends (El, E2) in the area of said discontinuation (D), the said free ends (El, E2) being situated at a distance from each other when the ring (S, S' ) is unmounted. 3. Sliding vane motor according to claim 2, c h a ¬ r a c t e r i z e d i n that the rings (S, S' ) are substantially circular and dimensioned such that they are pressed together somewhat by the circular cylindrical sealing surfaces (44, 45) of the housing, so that the opposite ends (El, E2) of the respective ring are situated closer to each other than when the rings are unmounted. 4. Sliding vane motor according to anyone of claims 1 to 3, c h a r a c t e r i z e d i n that the first and the second sealing surfaces (G, G' ) of the rotor body (R) have a diameter which is different from the diameter of the rotor body (R). 5. Sliding vane motor according to anyone of claims 1 to 4, c h a r a c t e r i z e d i n that the first and the second sealing surfaces (G, G' ) of the rotor body (R) have a diameter which is smaller than the diameter of the rotor body (R). 6. Device for automatic removal of a milking means ( 6) from the teats of an animal after finished milking, comprising a stand (1 ) and an actuation means (2) carried by the stand and having a rotatable cord drum (20) , a cord ( 13) windable onto the cord drum and being provided with a connection means ( 14) at its free end for connection to the milking means to be removed, and an actuation means (19, 21) provided to turn the cord drum (20) for winding the cord thereon, whereby the cord pulls the milking means off the teats of the animal when the cord drum (20) is turned by the actuation means (19, 21), wherein the actuation means (19, 21) comprises a sliding vane motor (19) according to anyone of claims 1-5.

Inventors: OLOFSSON HANS, OLOFSSON, HANS
Applicants: OLOFSSON HANS, TETRA LAVAL HOLDINGS & FINANCE, OLOFSSON, HANS, TETRA LAVAL HOLDINGS & FINANCE S.A.
Application year: 1994
Main classification: F01C1
IPC codes: A01J5, A01J7, F01C1, F01C19